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A Guide to Genetic Testing

Recently, we had a webinar on the genetics of HLH, part of which touched on genetic testing to receive a diagnosis or pinpoint a mutation. In histiocytic disorders, genetic testing can help bring someone a clear diagnosis. One important aspect of the work of the Histiocytosis Association is to help provide resources and information when you need it. To do this, we often will reach out to other organizations or programs to learn as much as we can, then share that information out in the best way possible. In this blog post, we will be going through some of the basics of genetic testing, and some specific organizations that can help histio warriors (and those of all rare diseases) with genetic testing.

Spotting a mutation in a genetic strand
Spotting a mutation in a genetic strand

According to, genomic profiling is “a laboratory method that is used to learn about all the genes in a person or in a specific cell type, and the way those genes interact with each other and with the environment.” For histiocytic disorders, genetic testing to look for genetic mutations may be suggested by your physician, or you may want to discuss this as a possibility if it has not been suggested. Upon identifying whether or not a person diagnosed with histiocytosis has a genetic mutation, decisions can be made about course of treatment; other members of the family may also consider genetic testing.

For histiocytic neoplasms (LCH, ECD, RDD), treatment options that may be considered include targeted therapies which attack specific genes or protein in the cancer cells. For histiocytic disorders, these targeted therapies include BRAF-Inhibitors and MEK-inhibitors, however many of these treatments are still only available through clinical trial. These therapies may be considered as a first line treatment option, or considered only after other conventional treatments are unsuccessful. Targeted therapies are likely required to be taken for a long time, as there is concern that the histiocytosis will recur upon stopping the drug.

Primarily, patients can ask their physician to help them in accessing genetic testing while being treated as an inpatient at their local hospital. Many hospitals have organizations/laboratories that they typically run their testing through, however turnaround times may not be expedited so patients should advocate for what they know will be best for them. When being treated as an outpatient (not staying overnight in the hospital) insurance coverage will be needed for most genetic testing. This would also be true for any family members who are hoping to receive testing however have not been diagnosed.

Genetic somatic mutations in histiocytic disorders
Somatic mutations in histiocytic disorders

In cases where it is not covered or a second opinion is being sought, you can try these other resources below:


The Memorial Sloan Kettering Make-an-IMPACT Initiative is a rare-cancer global outreach initiative that provides free genomic profiling for patients with Langerhans Cell Histiocytosis (LCH), Erdheim-Chester Disease (ECD), Rosai-Dorfman Disease (RDD), Juvenile Xanthogranuloma (JXG), and Histiocytic Sarcoma (HS). Genomic profiling with world class, next-generation sequencing technology developed at Memorial Sloan Kettering Cancer Center aims to identify genetic mutations in these tumors. These tumors often harbor mutations in BRAF or related family of genes and may respond to drugs that target these genetic alterations. Patients who were diagnosed or treated for LCH, RDD, ECD, JX, or HS within 2 years with current active disease may be eligible to participate. If you would like to learn more, please visit the Make-an-IMPACT site or reach out to the Make-an-IMPACT team: If you are eligible and would like to participate, please complete the volunteer form.

National Institutes of Health (NIH)

The Hematopathology Section of the National Institutes of Health provides consultation in selected cases of diagnostic difficulty and is pleased to assist patients with the diagnosis of histiocytosis, or suspected histiocytosis. Relevant diagnoses include Erdheim-Chester disease, Langerhans cell histiocytosis, Juvenile Xanthogranuloma, ALK-positive histiocytosis, Rosai-Dorfman disease, and Indeterminate cell histiocytosis. Other histiocytic neoplasms, histiocytic sarcoma, are accepted. View and/or download this list of instructions regarding cases to be submitted in consultation: Histiocytosis Registry And Genomic Studies; please share this with your physician.

You can also see our previous blog post on this subject here.

If you have any questions about genetic testing or genomic profiling, or any other testing that may be beneficial in determining treatment for you or a loved one, please do not hesitate to contact me at